MR angiographic findings of aberrant right subclavian artery with agenesis of the left common carotid artery and anomalous origin of the vertebral arteries.

Introduction: Congenital aortic arch anomalies and variants have been extensively characterized in the medical literature. Proper identification of these anomalies is important when surgical or percutaneous interventions are indicated.

Case Presentation: We present a case of a 48-year old male who presented to the emergency department with altered mental status.

Detection of subthreshold atrophy in crossed cerebellar degeneration via two-compartment mathematical modeling of cell density in DWI: A proof of concept study.

Crossed cerebellar diaschisis (CCD) refers to transneuronal degeneration of the corticopontocerebellar pathway, resulting in atrophy of cerebellum contralateral to supratentorial pathology. CCD is traditionally diagnosed on nuclear medicine studies. Our aim is to apply a biexponential diffusion model, composed of intracellular and extracellular compartments, to the detection of subthreshold CCD on DWI, with the calculated fraction of the intracellular compartment as a proposed measure of cell density.

An unusual case of cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy with occipital lobe involvement.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an autosomal dominant angiopathy caused by a mutation in the notch 3 gene on chromosome 19. Clinically, patients may be asymptomatic or can present with recurrent ischemic episodes and strokes leading to dementia, depression, pseudobulbar palsy, and hemi- or quadraplegia. Additional manifestations that have been described include migraine (mostly with aura), psychiatric disturbances, and epileptic seizures.

Cost analysis of vestibular schwannoma screening with contrast-enhanced magnetic resonance imaging in patients with asymmetrical hearing loss.

Background: Vestibular schwannomas are a rare cause of asymmetrical hearing loss, and routine screening with magnetic resonance imaging can be costly. This paper reports results on vestibular schwannoma screening at our institution and compares the cost of screening to a utility of hearing benefit.

Method: All screening examinations with magnetic resonance imaging performed for asymmetrical hearing loss between 2006 and 2011 were retrospectively reviewed.

The Revised Sonographic NASCET Index: A New Hemodynamic Parameter for the Assessment of Internal Carotid Artery Stenosis.

Purpose: A previously described Doppler parameter, the sonographic NASCET index (SNI), was derived to be more directly analogous to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) methodology for assessing carotid artery stenosis. However, this index does not account for complex changes affecting the Doppler waveform. We propose a revised SNI (rSNI) in an effort to improve predicting carotid stenosis.

A comparison of sagittal short T1 inversion recovery and T2-weighted FSE sequences for detection of multiple sclerosis spinal cord lesions.

Purpose: Multiple sclerosis (MS) is the most common disabling CNS disease of young adults. MRI is routinely used for the detection of MS plaques in the brain and spinal cord. A significant portion of patients with MS demonstrates spinal cord lesions at the time of initial workup, and these lesions are an important part of the McDonald criteria for diagnosis.

Complex imaging features of accidental cerebral intraventricular gadolinium administration.

Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) is a contrast agent commonly used for enhancing MRI. In this paper, the authors report on 2 cases of postoperative inadvertent administration of Gd-DTPA directly into a ventriculostomy tubing side port that was mistaken for intravenous tubing. Both cases demonstrated a low signal on MRI throughout the ventricular system and dependent portions of the subarachnoid spaces, which was originally believed to be CSF with areas of T1 shortening in the nondependent portions of the subarachnoid spaces, and misinterpreted as basal leptomeningeal enhancement and meningitis.

Parameter optimization for quantitative signal-concentration mapping using spoiled gradient echo MRI.

Rationale and Objectives. Accurate signal to tracer concentration maps are critical to quantitative MRI. The purpose of this study was to evaluate and optimize spoiled gradient echo (SPGR) MR sequences for the use of gadolinium (Gd-DTPA) as a kinetic tracer.

A medley of midbrain maladies: a brief review of midbrain anatomy and syndromology for radiologists.

The midbrain represents the uppermost portion of the brainstem, containing numerous important nuclei and white matter tracts, most of which are involved in motor control, as well as the auditory and visual pathways. Notable midbrain nuclei include the superior and inferior colliculus nuclei, red nucleus, substantia nigra, oculomotor nuclear complex, and trochlear nucleus. In addition, white matter tracts include the brachium conjunctivum, medial and lateral lemniscus, spinothalamic tracts, and the fiber tracts within the cerebral peduncles.

Dominant posterior-variant alien hand syndrome after acute left parietal infarction.

Alien hand syndrome (AHS) is a complex clinical disorder in which patients develop a sense of estrangement from, and loss of volitional control of, an affected limb and non-purposeful complex motor actions of the same limb. Several forms of AHS exist, including frontal, callosal, and posterior types with a series of different associated neuroanatomical lesions and clinical symptoms. Most commonly, the lesions associated with AHS occur in the frontal lobes and corpus callosum.

Cerebral toxoplasmosis: case review and description of a new imaging sign.

Toxoplasmosis can have catastrophic consequences in immunocompromised patients if left untreated. Accurate diagnosis is difficult, as there is substantial overlap between the imaging findings and presenting clinical syndromes of cerebral toxoplasmosis and primary central nervous system lymphoma. This paper reviews the previously described and fairly well-known post-contrast computed tomography (CT) and T1-weighted (W) magnetic resonance imaging (MRI) target signs seen in toxoplasmosis.

Midbrain ataxia: an introduction to the mesencephalic locomotor region and the pedunculopontine nucleus.

Objective: Although gait ataxia is usually associated with cerebellar lesions, we review a less familiar cause. We present three patients with dorsal midbrain lesions and correlate these presentations with recent findings in the functional anatomy of the midbrain.

Conclusion: We suggest that these lesions involve a well-studied but generally unfamiliar area of the dorsal midbrain known as the mesencephalic locomotor region.

Sonographic NASCET index: a new doppler parameter for assessment of internal carotid artery stenosis.

Background And Purpose: Established Doppler parameters for carotid stenosis assessment do not reflect North American Symptomatic Carotid Endarterectomy Trial (NASCET)-style methodology. We derived a Doppler parameter, termed sonographic NASCET index (SNI), and hypothesized that the SNI would provide greater angiographic correlation and better accuracy in predicting stenosis of 70% or greater than that of currently used peak systolic velocity (PSV) measurements.

Methods: Inclusion criteria of angiographically proved carotid stenoses of 40-95% and measured proximal and distal internal carotid artery Doppler PSV values were established.

Accuracy of contrast-enhanced MR angiography in predicting angiographic stenosis of the internal carotid artery: linear regression analysis.

Background And Purpose: We sought to assess whether contrast-enhanced MR angiography is able to predict the degree of angiographic stenosis of the internal carotid artery within a clinically acceptable margin of error, thereby decreasing the need for angiography. In addition, we sought to assess whether adding ultrasound peak systolic velocity (PSV) as an additional regressor improves the accuracy of prediction.

Methods: A retrospective review of our institution's records for a 4-year period was conducted to identify all patients who had undergone evaluation of their carotid arteries using digital subtraction angiography, contrast-enhanced MR angiography, and ultrasonography.

Imaging of the internal carotid artery: the dilemma of total versus near total occlusion.

Purpose: To evaluate ultrasonography (US) and magnetic resonance (MR) angiography in the differentiation between occlusion and near occlusion of internal carotid artery (ICA).

Materials And Methods: Consecutive patients with occlusion or near occlusion of ICA at catheter angiography and who underwent MR angiography and US were included. MR angiography and US were compared with catheter angiography, the standard, for the ability to help distinguish occlusion from near occlusion.

Systems analysis of functional magnetic resonance imaging data using a physiologic model of venous oxygenation.

The authors revisit a simple mathematical model, presented in previous work, that characterizes the response of cerebral venous oxygenation to changes in blood flow and oxygen consumption. This physiologically based model can qualitatively duplicate the results of several recent empirical studies in which other authors have tested the hypothesis of linearity in the functional magnetic resonance imaging (fMRI) response to task activation, in that the experimentally found nearly linear behavior of the system and also its subtle departures from linearity are both predicted by simulations of the model. The model is simple enough that its equations can be explicitly solved.

Mesiotemporal T2-weighted hyperintensity: neurosyphilis mimicking herpes encephalitis.

Bilateral mesiotemporal hyperintensity on T2-weighted and fluid-attenuated inversion recovery MR images of a patient with a clinical syndrome of encephalitis is considered to be a classic finding for herpes simplex virus infection. We report a case of neurosyphilis with identical MR imaging abnormalities and a similar clinical presentation. Because syphilis is not routinely tested for, awareness of this mimicry of herpes simplex virus encephalitis is important, considering the potential therapeutic implications.

Ability to use duplex US to quantify internal carotid arterial stenoses: fact or fiction?

Purpose: To determine if duplex ultrasonography (US) can help predict the degree of internal carotid arterial (ICA) stenosis.

Materials And Methods: ICA peak systolic velocity (PSV) and the ratio of the PSV in the ICA to that in the ipsilateral common carotid artery (VICA/VCCA) were compared with the degree of arteriographically measured stenosis. ICAs were arteriographically subgrouped at 10% incremental levels of stenosis and broader ranges.

Doppler sonographic parameters for detection of carotid stenosis: is there an optimum method for their selection?

Objective: A wide range of Doppler threshold values for carotid stenosis is found in the literature. We undertook this study to compare methods of derivation and to determine if an optimum strategy of threshold selection exists for a high-risk population.

Materials And Methods: From the sonograms of all patent internal carotid arteries, peak systolic velocity in the internal carotid artery (ICA(PSV)) and the ratio of peak systolic velocity in the internal carotid artery to that of the common carotid artery (ICA(PSV)/ CCA(PSV)) were compared with the percentage of angiographically determined stenosis.

The early response in fMRI: a modeling approach.

A mathematical model is presented to study the generation of the early response phenomenon in fMRI. Initially, we demonstrate that a simple combination of the changes taking place in cerebral blood volume and flow could create the transient early signal decrease, by analyzing their effects on total per voxel deoxyhemoglobin content. Also, we examine the traditional paradigm for the early response: that it may be caused by an early burst of oxidative metabolism and conclude that such changes also explain the early transient response.

The lag of cerebral hemodynamics with rapidly alternating periodic stimulation: modeling for functional MRI.

A mathematical model that characterizes the response of venous oxygenation to changes in cerebral blood flow (rCBF) and oxygen consumption has been previously presented. We use this model to examine the dampening phenomenon in functional MRI (fMRI) signals with rapidly alternating periodic stimulation bursts. Using a mass balance approach, the equations for an input-output model are derived and solved using Matlab (the Math Works Inc.